The present invention relates generally to the sensing and measurement of strain.
The sensing of strain by measuring changes in electrical impedance of a magnetostrictive body of material under stress, to which a magnetic field is applied, is generally known in the art as disclosed in U.S. Pat. Nos. 3,745,448, 4,500,864, 5,142,227 and 5,168,760 to Hiratsuk, Nakaue et al., Fish and Wun-Fogle et al., respectively. According to the Fish patent, the magnetostrictive body of material in the form of a wire, ribbon or thin film is subjected to strain measured as changes in electrical resistance. According to the Wun-Fogle et al. patent, the electrical resistance of ferromagnetic material subjected to a magnetic field, is measured in order to provide data to a strain indicator. Such prior art strain sensing and gauging systems are often limited as to application, and are relatively costly because of data processing necessary in connection therewith.
It is therefore an important object of the present invention to provide a system for sensing strain in a wide variety of applications by measurement of the impedance of a relatively small magnetostrictive body of material such as wire, ribbon, film or the like, with a high degree of sensitivity so as to enhance determination of strain in a less costly manner.